There are currently produced large five gallon molded plastic lids for use with five gallon containers filled with various contents, often liquid contents such as paint. These large lids are relatively strong in that the plastic used therein must support the weight of a series of stacked containers thereabove during warehousing or transporting. The weight can be as much as four hundred pounds. These lids are provided with relatively thick and strong skirts or peripheral flanges that have a locking ring engaging a locking bead on the container. A typical drop test is to drop a fully loaded container four feet and then to test for the integrity of the lid and its seal with the container. Such container lids are often 12 inches in diameter. The lid usually contains slots or areas of weakness in the skirt flange for breaking of the lid into a plurality of segments. Often, slots in the form of screw driver slots are present in the outer surface of the skirt flange and a screw driver is forced into a slot and used as a lever to fracture the skirt flange into a plurality of segments each of which still has a locking ring segment in full locking or sealing engagement with the container bead. With considerable exertion of force, several of the flange segments are pried outwardly to shift radially outwardly their associated locking ring segments and these flange segments are bent upwardly to cam their locking ring segments across the container bead. Then, the remainder of the lid is bent and rolled and pried to cause the other locking ring segments to slide across and over the locking bead until the lid is freed. Tools such as pliers are often used to pull and pry the flange segments outwardly and to peel their locking ring segments across the container retention bead. Such lids are difficult to remove even with tools.
U.S. Pat. No. 4,735,337 proposes an easier opening lid than above-described by providing a tear strip that removes one half of the flange segments which then must be pried over the container bead. In a second embodiment of this '337 patent, half of the flange segments are pivoted upwardly about a line of weakness, while the other half of the flange segments without a line of weakness remain in engagement with the container bead. The removal of the lid requires the simultaneous outward deflection of these remaining flange segments, while at the same time lifting up on the lid. The outward deflection must be sufficient to disengage the gripping locking ring portions from the annular bead or shoulder provided on the outer periphery of the upper edge of the container wall.
Upon reuse of the above described lid of the '337 patent, the lid is forced back on to the container with sufficient force to deflect the remaining flange segments outwardly whereby the gripping locking ring portions may reengage with the underside of the shoulder or bead on the container. Because of the large diameter of such plastic lids, it is difficult to overcome the friction associated with the engaging cylindrical surfaces on the container and lid in replacing the lid to its sealed position. The force associated with deflecting the remaining flange segments in replacing the lid adds significantly to the problem of reattaching the lid. In addition, there is often dried paint or other container contents that may have been deposited on these engaging surfaces of the lid and container that are likely to increase the force necessary to reattach the lid to the container.
It is also difficult to determine when or if the lid has been forced down sufficiently to reengage the gripping projections under the bead. If such reengagement is not accomplished, there will not be an acceptable seal formed between the lid and the container.
Another patent showing the use of a plastic lid having peripherally spaced fold-out flange portions is Blair U.S. Pat. No. 4,055,267. The Blair patent would not be suitable for providing a resealable positive seal.